How should the common-mode inductor of a concentrator be matched?

When selecting a common-mode inductor for a concentrator, the interference frequency band, impedance requirements, and circuit current matching parameters must be considered. If the target suppression frequency band is 150kHz-1MHz (switching power supply noise), a high-inductance inductor should be selected, such as CMZ1211-501T (500μH). For higher frequencies (e.g., above 30MHz), the high-frequency impedance curve of the inductor should be considered, and CMZ2012A-900T (90μH, Z>800Ω at 100MHz) should be selected. The rated current must be greater than the maximum operating current (including peak value) flowing through the inductor, with a 50% margin.

For example, if the main power supply current is 2A, a model with a rated current of 3A or higher should be selected. DC superposition characteristics should also be considered to ensure that the inductance value attenuation does not exceed 20% under high current. Structurally, models with symmetrical windings and small inter-turn capacitance should be selected to reduce differential-mode to common-mode conversion. During installation, the inductor should be kept at least 5mm away from surrounding components (especially Y capacitors). A well-matched common-mode inductor combined with a Y capacitor can provide more than 40dB of common-mode insertion loss from 1 to 30MHz.